Synopsis: Noah is, obviously, Russell Crowe, a chunky eco-warrior battling to save the world – or, because the world is filled with selfish fools, just his family and a few furry and feathered friends – from imminent destruction. The result of mankind's careless, wilful attitude to Earth's bounty. He's up against Ray Winstone, speaking in his best telephone voice, as a flood-denier and rival to God. Or so I roughly make out from the trailer for Noah, the movie, and a few teaser interviews with director Darren Aronofsky, who describes it as "the least biblical biblical film ever made".

There are people who are cross about the movie and what its makers call the "artistic licence" that has been taken with the Bible narrative. But then there are always people who are cross, especially when it comes to the Bible. Mostly they are extremist believers of one sort or another, the more literalist of the peoples of the book: Jews, Christians, Muslims. I'm not a believer, and my only problem with artistic licence is when the phrase is used as an excuse to oversimplify a work to improve its marketability.

But I am a reader of the Bible. The Bible isn't the word of God or dictation taken by any of his followers, but neither is it a novel, though it is a kind of structural matrix for all fiction. It is a most extraordinary text written by several hands from different periods, each having their own motives and style. The story of Noah is written by two sources – the "J" writer, older and more folkloric, and the "Priestly writer" most interested in getting Judaism into a regular religious shape – both of which have been plaited together as best they could by later editors. At its most thrilling, the text is more minimalist than Beckett and sustains as microscopic a reading as Emily Dickinson's poetry. It's like a jigsaw puzzle of a distant garden which when fitted together opens out into as many blooms as you can bear to entertain. It is the Tardis.

It's not just me. For many hundreds of years, rabbis have been discussing their interpretations of the most minute clues in the text. Most of all they love to elaborate on what is not there, and, like all humans, try to make sense of contradictions, implausibility, reticence, and to uncover and make meaningful, as if it were Twitter, more puns than you can shake an olive branch at. The bellowing and infighting on paper that had been going on since the Hebrews returned from their exile in Babylon, was collected and edited in the early Middle Ages into various books of midrash: interjections, extrapolations, interpretation, each devoted to the books of the Bible.

And it continues today, the discourse and the amiable discord, by turns legalistic, linguistic, poetic, artistic, metaphysical, practical, transcendental, earthy, comedic. If it worries you, get to the bottom of it. For example, what about the fish? Didn't God say he was going to destroy all life on Earth, animal and human? So what about the fish? How is a flood going to harm them? There's a midrash for that. The deluge was hot rain, so the fish cooked. Ta-da!

Then again, and of course, there's another midrash: no, the fish didn't die, because God said, if you don't mind reading properly, he would destroy all he had created "from the face of the Earth". The fish, in the sea, were exempt. No mention of amphibians, one of those nasty ambiguities that Leviticus hates so much, both one thing and another (which makes any combination in a single thing unclean: clothes made of two kinds of fabric, animals that breed with other species), but the amphibians would surely have decided to take the watery route to survival.

Woodcut from Liber Chronicarum Mundi, 1493. Photograph: Getty

The absence of fish in Noah's story set the medieval rabbis stroking their beards and thinking hard. There are so many absences in the story of the Flood. The greatest of them is Noah himself. From the moment God speaks to him until he leaves the ark and steps on to dry land, he never says a word. Most importantly, he does not reply when God tells him that he is going to destroy all living creatures except Noah and his family. Noah expresses no shock or horror at the idea of the mass destruction of the Earth and its inhabitants. Nor does he plead with God to think again, to give human and animal kind another chance. Even Abraham, that apparently super-obedient servant of God, who seems not to demur when commanded to kill his own son, even he stands up to God at the prospect of the destruction of Sodom. "That be far from thee to do after this manner, to slay the righteous with the wicked … and that the righteous should be as the wicked, that be far from thee: Shall not the Judge of all the earth do right?" Abraham, so painfully obedient, dares to confront God and teach him a lesson in equity and justice.

Noah says not a word. He receives his orders to build the ark and sets about it. He is a man, it seems from his silence, from the Bible's silence, without concern for others, lacking empathy, or even curiosity as to why exactly he alone has been saved to remake the world and become the second Adam. All we are told is that God regrets having made men, that they were constantly evil, and "Noah found grace in the eyes of the Lord … Noah was a just man and perfect in his generations, and Noah walked with God".

The rabbis have a field day with this. They can't forgive him for his silence and acquiescence. "Perfect in his generations" means simply that he was only just OK, compared to the dreadfulness of the rest of his cohort. Finding grace in the eyes of the Lord suggests that there is no intrinsic grace in Noah; God chose him, almost as if he stuck a pin in a list. Noah is no hero, not chosen for his specialness. He walks "beside" God, whereas Abraham is permitted to walk actively "before" him, a doer in the world. Noah is apathetic, lacks vivacity, yet God, in choosing him, shows an irrationality we have seen before in Genesis (favouring Abel's offering over Cain's and setting up the first motive for murder, for example). Perhaps, at best, he is chosen for his blankness, for being all potential.

As well as condemning Noah, the ever-querulous rabbis offer him a let-out. Noah, they say, planted the seeds of the cedar trees he needed to make the ark and waited 120 years for them to grow. Why? So that men would have a chance to ask him what he was doing. This is a poor recuperation of his character. Why not just warn them? The answer to that presumably is the brand new midrash of Noah-the-movie: Ray Winstone would only come and shout at him that he was talking rubbish, then set his hoard of CGI'd supporters against him. As I said, midrash goes on.The joys of the black holes of biblical storytelling also go on.

The text of the bible is spare in both words and emotions. But it's a text that knows it will be read by us and that its eloquent silences will beg questions that rabbis, writers, readers, film-makers, all being human, will dive into in search of extrapolation. Like children being told a bedtime story. Tell me more! And: Why?

God tells Noah that men and women are to go in separately, and the male and female animals are also to be segregated. Sex is out. There will be none of that sort of thing until the ark floats back down to earth. It's quite sensible under the circumstances. There's Noah and his wife, his three sons, Shem, Ham and Japheth, with their wives, all together for a year on a yacht filled to over-capacity with animals on one floor, the humans on another and dung on the ground floor. It needs self-control to cope with such living accommodation, without adding sex into the mix, let alone whatever offspring would have resulted. Though the overpowering stink surely would have reduced carnal impulses. It seems from the rabbis that what had been annoying God in the first place was the outlandish sexual goings-on. Not just men with women and those combinations, but humans with animals and animals with animals of different species.

In any case, Noah, at least, wouldn't have had time for sex. It turns out, inside a void in the narrative, that he didn't get a wink of sleep, from the moment he boarded the ark to the moment he left it. An entire year without sleep, because it was his job to feed the animals. He had to learn their schedules and preferences. Some ate by day, some by night. And they all had to be kept alive and contented. At last we begin to watch Noah learn how to know and care for others.

Avivah Zornberg, in her remarkable collection of lectures on Genesis, The Beginning of Desire, writes: "The ark becomes a crucible in which a new type of sensibility is nurtured… The ark is to be a laboratory of kindness." She explains that the ark in Hebrew can also be translated as "box". It is a prison, too (if it doesn't become a grave), from which the birds are released to find out what is happening in the world. First the raven, who complains, "Why me?" "Because," Noah says in a midrash, speaking as the rabbis need him to, "nobody likes you. You're no good to eat or to sacrifice. Get going!" The doves, of course, are much more well-behaved and do what they are told, cooing placidly.

A 19th-century American engraving. Photograph: Apic/Getty Images

Back on dry land, Noah makes a sacrifice to God in gratitude for their survival. He seems to have learned some humane sensibility, but not enough to make him enraged on behalf of the dead masses. But God has done some learning himself. He has realised what he's dealing with in mankind, and thinks, without saying it to Noah: "I will not again curse the ground any more for man's sake; for the imagination of man's heart is evil from his youth, neither will I smite any more every thing living, as I have done."

They – we – are just not worth the trouble. It'll just be the same, over and over again. So he blesses Noah, and gives him some rules: now instead of Adam being simply in charge of the beasts, Noah is told that they will fear and dread him. And as well as the vegetation given to Adam for sustenance, Noah can eat any of the animals. Meat-eating has arrived, suitable for the savagery of God's creation, though it must be bloodless. One other thing, man should not be killed and if he is – which he will be given his nature – the killer's blood must be shed, too.

Finally, he makes a promise to put a rainbow in the sky as a covenant with man, and to remind himself that he may never destroy the world again. He doesn't mention that he has understood that men are incorrigible. Perhaps he thinks that they can be trusted to destroy the world themselves. It has been an educational experience for God as well as Noah, but perhaps he has learned the opposite of empathy. He distances himself rather, though he does still need a reminder not to smite Earth's entirely smite-worthy inhabitants.

People complain that there are no laughs in the Bible (actually Sarah, the wife of Abraham, fails to conceal her amusement when she's told that she's about to conceive, at the age of 90: "Therefore Sarah laughed within herself… And the Lord said unto Abraham, Wherefore did Sara laugh…"), but let the rabbis loose on it, and it's practically standup material. Even the rabbis, though, fail to squeeze much in the way of laughs out of the coda to Noah's story. One of the things the Christian evangelicals complained about in Aronofsky's film was a scene in which Noah gets drunk. Which is odd, because he may not have been an eco-warrior hero in the biblical story, but he certainly did get drunk. In fact, he planted the world's first vineyard, and then took a fancy to its produce. "And he drank of the wine, and was drunken; and he was uncovered within his tent."

Who would blame him for going on a bender after a year cooped up, everyone and everything drowned, and having to make a new world? Still, it's not exactly an heroic ending. He planted a vineyard, not the most useful of things with which to restart civilisation, and then lay sottish and naked in his tent. You or I might do that, but God's chosen new Adam? Midrash suggests that the fruit of the tree of which Adam was forbidden was, in fact, a vine. Is the story telling us it's just what people do, and all men, as God has realised, are hopelessly flawed? Or was he a broken man – was his guilt at not trying to save his fellow man too great to bear sober? Was getting drunk the result of his inability to mourn, a Freudian failure to acknowledge the reality of loss? Was he suffering survivor guilt, with reason enough to want to dull the pain?

There would be a real ring of truth about this if it were in fact the ending of Noah's story. The invention of the antihero, long before the 1950s revived the concept. But it isn't the end. The ring of truth falls silent when Ham wanders into his drunken father's tent.

Ham, who was the father of Canaan, walked into the tent and "saw the nakedness of his father, and told his two brethren without". For which, when he regained his senses, Noah cursed Ham's son, Canaan, and condemned him to become the servant of Shem and Japheth and their offspring. Shem and Japheth had walked backwards into the tent with a garment over their shoulders and, without looking behind them at Noah, covered him and "saw not their father's nakedness". So why the gravity of Ham's punishment? Baffling. Perfect for the rabbis to work on, but difficult or embarrassing enough for most of them to keep their silence.

It isn't the most famous part of the Noah story. Not the one they tell in primary schools where the animals walked in two by two. There's no tiny figure of the naked Noah in a stupor in those wooden sets of Noah's Ark. Perhaps, suggests the Gemora Sanhedrin, facing up to the oddity of the verse about Ham seeing his father's nakedness, it means either that Ham castrated his father, or that he sodomised him. This seems a bit of a stretch from "seeing his nakedness", but we know the Bible has a quaint way with sexual deeds: lying with each other, knowing each other – and why would Ham's offspring be condemned to servility for an innocent incident?

I wonder what the movie will make of this. Beyond their disapproval of showing Noah drunk, there are no mentions of incest or Oedipal activity in reports of complaints about the movie from the fundamentalists. Maybe the movie ends with the rainbow promise and a drunken I Will Survive party. I wonder what the fundamentalists make of this passage in the Bible. Either option, castration or sodomy, certainly seems an ignominious finale to the Noah, with whom the world began again. The Bible has no more to say after the curse, beyond "And Noah lived after the flood three hundred and fifty years. And all the days of Noah were nine hundred and fifty years: and he died."

Perhaps it simply goes to show how right the Lord was to give up hope in mankind's essential goodness. Or, as is the way of the Bible and in particular the Priestly writer's text, it was simply having one of its expositional geopolitical history moments, to explain why the Canaanites (with Noah's curse on them) had to vacate their land so that the tribe of Israel could move in and settle there. Nothing to do with sex, but a florid way of giving grounds for how things got to be the way they are, and ever should be. Just as Israel today chooses to explain its land "rights" on the basis of that ancient, patched-together, fanciful book.

A great read, and a delightful puzzle, but as the contradictory and whimsical interpretations of the rabbis show, hardly a reliable basis for justifying real-world land grabs. Dubious folk-historical territorial claims, on the one hand; an ancient parable to warn of the next man-made destruction of the planet modern, on the other. I look forward to what the least biblical of biblical films will do with this most malleable of texts.